| Shredded squid as a popular snack food is rich in trimethylamine-n-oxide (TMAO). TMAO can be decomposed to equimolar formaldehyde and dimethylamine (DMA) by certain ways, but the presence of formaldehyde would affect the quality of shredded squid. Up to the present, methods for the determination of formaldehyde only include free and reversible parts, which can not be a true reflection of the formaldehyde content in aquatic products. The amounts of DMA and formaldehyde are produced equally, so the amount of DMA can indirectly reflect the real content of formaldehyde. In addition, trimethylamine (TMA) with the smell of corruption is also one of the degradation products of trimethylamine oxide, and TMA and DMA are precursors of carcinogenic N-nitroso amine. Therefore, the detection of TMAO, TMA and DMA content in the aquatic products do great significance toward evaluating quality of shredded squid, squid and other seafood.In view of these situations, an ion chromatography method for determination of TMAO, TMA and DMA in the aquatic products was established. Parameters of this method were discussed. Then some differences of ion chromatography and regular method of spectrophometer had been compared. Based on this new approach, the influence of NaHSO3 toward the changes of formaldehyde, TMAO, TMA and DMA were studied during the process and storage stage of squid. Finally, maillard reaction as a possible production way of formaldehyde during the process and storage stage of squid was studied.The main results obtained in this study were as follows.1. An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of DMA, TMA and TMAO in aquatic products. The analysis conditions were: mobile phase: 3.0 mmol/L methanesulfonic acid; flow rate: 0.8ml/min; injection volume: 25μL; Column temperature: 30℃; conductivity cell temperature: 35℃. The retention times of DMA,TMA and TMAO were 11.89, 14.37 and 15.31 min, respectively. Detection limits of DMA, TMA and TMAO were 0.06, 0.06 and 0.10 mg/L, respectively. Recoveries were between 93.8% and 104.1%. The relative standard deviations (RSD) were between 0.54% and 3.53%2. The methods between ion chromatography and spectrophotometer for determination of TMAO, TMA and DMA in samples were compared and found their results were similar, but the method of ion chromatography for simultaneous determination of TMAO, TMA and DMA significantly shorten the analysis time, had a higher sensitivity and a simple pre-treatment of samples.3. NaHSO3 as an immersion solution applied in earlier processing and an adsorbent applied in storage of shredded squid for controlling the formaldehyde content of squid product were studies. After application in processing, the content of TMAO in treated group reduced third than control group in the final product but the quantity of formaldehyde were gererated more than the control group. The result of NaHSO3 applied in storage showed that the content of formaldehyde in all treated groups was dropped as a whole and the content of TMAO also had a declined trend during the storage, while the amounts of DMA and TMA were increasing.4. TMAO-lactose in vitro was operated and found that formaldehyde can be generated by Maillard reaction. The changes of related substances in shredded squid were compared before and after storage, the results showed that the generated formaldehyde in the storage of shredded squid was related to the maillard reaction between lactose and TMAO. The changes of related substances in four kinds of shredded squid were also compared during the processing and storage, the results further indicated that the increasing amount of formaidehyde in the processing and storage was related to maillard reaction. Therefore, the methods for controlling the Maillard reaction are the way to control formaldehyde. |
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